In small-incision endoscopic surgery, small incision wounds are made at several places in the chest or the abdomen, and the surgery is performed using a surgical instrument such as forceps or an electric knife while the inside of a body cavity is viewed with a thoracoscope or a laparoscope. Accordingly, compared with thoracotomy/laparotomy in which a large incision is made, postoperative pain is very little and also the scar is substantially inconspicuous. Therefore, invasiveness of the surgical treatment can be significantly reduced, and at the same time, the quality of life (QOL) can be greatly improved.
In such small-incision endoscopic surgery, the surgical field is often ensured by: a surgical instrument having a hook-shaped leading end being inserted from the small incision wound; and a surgical assistant pulling, by hand, the leading end of the surgical instrument hooked on a surgical incision in the body (hereinafter, this operation will be referred to as “incision using a traction hook”).
In addition to the incision using a traction hook, retractors using elastic plate-shaped bodies are used for ensuring the surgical field. Here, those retractors are not for use in small-incision endoscopic surgery (see FIG. 1 to FIG. 5 of Patent Literature 1 and FIG. 4 of Patent Literature 2, for example).
In Patent Literature 1, a retractor is formed into a cylindrical shape with a large outer diameter by being rounded so that the front end and the back end thereof are slidable. The entirety of the retractor is rounded into a small cylinder of a small diameter, and is then inserted into a surgical incision. The retractor expands due to elastic force in the surgical incision, thereby widening the surgical incision.
In Patent Literature 2, a shape memory alloy that has a shape memory property at a living-body temperature (about 37° C.) is formed into a plate shape, and then, the resultant shape memory alloy is caused to memorize a cylindrical shape with a large outer diameter, to obtain a retractor. The entirety of the retractor is rounded into a small cylinder with a small diameter, and is then inserted into a surgical incision. The retractor expands in the surgical incision due to the shape memory effect caused by the body temperature of the patient, thereby widening the surgical incision.